Recently, a technique has generally been known that creates a ship track of a ship based on data obtained from an Automatic Identification System (AIS) or the like. Also, a technique has generally been known that connects positions of ships at an identical point of time with a line segment by using a plurality of created ship tracks, so that a positional relationship between the ships is visualized. Such a technique is used so as to connect positions of ships at an identical point of time with a line segment, and thereby, a case where a risk of collision is estimated to be high, such as a case where ships cause abnormal closeness therebetween or a case where avoidance behavior is made to avoid collision therebetween, can be indicated. For example, a result of such visualization can be utilized for further testing or determination as to whether a risky case is caused, and extraction of such a case.
Japanese National Publication of International Patent Application No. 2008-514483
However, it may be impossible for a related technique to readily extract a case where a risk of collision between ships is estimated to be high. For extraction of a case where it is estimated that a risk of collision is high and avoidance behavior is made, for example, in a related technique, as positional information of each ship is acquired at a small time interval and respective positions of ships at each point of time are connected with a line segment, many line segments are displayed at a small interval, and hence, it may be impossible to readily determine whether a ship makes avoidance behavior thereof.
Herein, a method can be considered that connects respective positions of ships with a line segment at a large time interval. However, as respective positions of ships are connected with a line segment at a large time interval, for example, positions of ships at a point of time when it is estimated that the ships are closest to one another and a risk of collision therebetween is high may be unconnected with a line segment. Hence, it may be impossible to readily determine whether a ship makes avoidance behavior thereof.
Thus, in a related technique, even in a case where a positional relationship between ships is visualized, work to extract a risky case where a ship makes avoidance behavior thereof is cumbersome and it may be impossible to readily extract such a case where a ship makes avoidance behavior thereof.
In a first idea, a ship track data display program causes a computer to execute a step of extracting particular ship track data for a set of particular ships with a relative distance therebetween being within a predetermined range, from ship track data for a plurality of ships. The ship track data display program causes a computer to execute a step of extracting a place where a distance between ship tracks thereof is at a local minimum, from the particular ship track data. The ship track data display program causes a computer to execute a step of associatively displaying, for the extracted place, point data of a ship that previously arrives at the extracted place, in the set of particular ships, and point data of another ship at a point of time when the ship that previously arrives at the extracted place arrives thereat.